The sheep that will not die

Clinging
to the myth of Audubon’s bighorn.By Brett French

This story is featured in Montana OutdoorsNovember–December
2004

Can a species be extinct if it never existed? With the bicentennial of the
Lewis and Clark Expedition now under way, Audubon’s bighorn sheep are
often mentioned as one of the now-extinct species the Corps of Discovery
encountered on its trip up the Missouri River. “The Mandan Indians
Call this sheep Ar-as-ta,” Clark wrote on December 22, 1804, while
camped in what is today central North Dakota. “It is about the size
of a large Deer, or a small Elk, its Horns Come out and wind around the head
like the horns of a Ram….”

But did expedition members actually see a unique sheep subspecies, or,
as new re-search indicates, did they simply come across a variation of the
widespread Rocky Mountain bighorn that, at the time, lived farther east than
it does today?

What did they actually see?
There is no debate that bighorn sheep once existed farther east from their
current range. Biologists believe the sheep likely settled in the northern
Great Plains badlands over millennia by migrating from the Rocky Mountains
down the Missouri and Yellowstone rivers, slowly expanding up tributary
drainages.

Lewis and Clark encountered their first bighorn sheep in eastern
Montana, killing three in what is today the Upper Missouri River National
Monu-ment. A year later, on his return trip down the Yellowstone River,
William Clark noted in his journal that the party saw “a gang of
about 40 Big horn” sheep, and he killed four after inscribing his
name in the sandstone of Pompeys Pillar.

While retracing the Lewis and Clark Expedition’s route in 1843, noted
naturalist John James Audubon hunted bighorn sheep in the badlands of North
Dakota and wrote about his experience. In 1901, perhaps in honor of Audubon’s
observations, natural historian C. Hart Merriam scientifically classified
the badlands sheep as a subspecies of Rocky Mountain bighorn (Ovis canadensis)
and called them Ovis canadensis auduboni. The name gained even greater scientific
credence in 1940, when the esteemed Canadian zoology professor Ian McTaggart-Cowan
included the Audubon’s as one of seven subspecies of bighorn sheep
he de-fined in North America.

It took thousands of years for bighorn sheep to explore, claim, and settle
the badlands, but the animals were removed from the region in less than 100
years. The westward expansion of land-hungry Americans and immigrants quickly
displaced the big-horn sheep in eastern Montana and the western Dakotas and
Nebraska. The sheep were hunted for food and, later, their elegant curled
horns. Then, as sheepherders and cattlemen moved in, the bighorn’s
range was overtaken by livestock that carried diseases for which the native
sheep had no immunity. Finally, cheap land offered to those who would settle
and cultivate the ground brought a rush of farmers to the dry lands.

Squeezed by the pressures of western settlement and expansion, bighorn sheep
living in the badlands died out. In his book Lives of
Game Animals, published
in 1929, naturalist Ernest Thompson Seton noted that bighorn sheep were “practically
cleared out of the Black Hills by about 1887, though… a few lingered
on till 1899 when the last one was killed.” The last bighorn sheep
seen in eastern Montana was a ram killed in 1916 in the Seven Blackfoot Creek
area of the Missouri Breaks.

Questioning a classification
For nearly a century after the Missouri Breaks ram was killed, biologists
and others have lamented the disappearance of the so-called Audubon’s
bighorn. As one North Dakota state publication puts it, “Thus, the
Audubon [sic] bighorn went the way of the passenger pigeon and Carolina
parakeet.”

And yet new evidence seems to show there never was a separate Audubon’s
bighorn subspecies. These great sheep of the Great Plains were simply Rocky
Mountain bighorns that had adapted to life at lower elevations.

A species is a population with roughly the same size, color, behavior, and
habitat that breeds with each other and can’t breed with other groups.
Members of the Canada goose species, for example, can’t breed with
those of other waterfowl species, such as the snow goose.

A subspecies is a race or group within a species that looks and is genetically
different from other members of the species but can still breed with them.
For example, there are several subspecies of Canada geese that differ mainly
in size. And scientists have concluded that the Rocky Mountain bighorn and
the desert bighorn are different subspecies.

The big question is whether what has been called the Audubon’s bighorn
sheep differed enough from ordinary Rocky Mountain bighorns to be considered
a subspecies.

Biologists don’t dispute that the badlands bighorns may have looked
slightly different from their mountainous cousins. But those minor differences
weren’t enough for population research scientists John Wehausen and
Rob Ramey. In a study published in Journal of Mammalogy in 2000, they wrote, “Our
results did not support the recognition of Audubon’s bighorn sheep
as a subspecies separate from Rocky Mountain bighorn sheep….” The
scientists noted that Cowan’s classification of the Audubon’s
60 years ear-lier was based on examination of just four bighorn skulls, and
they took issue with the fact that the “type specimen” was not
an adult ram but a juvenile. “The resolution and results were influenced
by small samples, age-related effects on size, and violation of statistical
assumptions,” they wrote. “As a result, statistical re-analysis
of Cowan’s (1940) original data has not found support for most of his
subspecific designations.”

Taxonomy in the early 20th century was fraught with subjective interpretations
of limited information. “In traditional taxonomy, species and subspecies
were what a good taxonomist said they were,” says Ramey, chair and
curator of vertebrate zoology at the Denver Museum of Nature and Science.

For their study, Ramey and Wehausen were able to find seven alleged Audubon’s
specimens—two adult male bighorn skulls from North Dakota, two from
South Dakota, and three from eastern Montana. They used 50 measurements to
describe four skull attributes: lengths, widths, height, and horns, and then
measured each horn using five circumferences to determine volume. The researchers
found “no significant differences” between those skulls and those
of ordinary Rocky Mountain bighorn sheep.

“It’s really not a very surprising result,” says Wehausen,
a scientist at the University of California White Mountain Research Station. “We’re
just correcting some questionable work from earlier days. Now we have more
rigorous hypothesis testing.”

Modern scientists also point out that no reasonable evolutionary explanation
exists to explain a distinct subspecies of bighorn sheep. The badlands sheep
were never geographically separated from the Rocky Mountain bighorn sheep.
Biologists say a newly formed natural barrier would have been necessary to
isolate the badlands bighorns so they would develop distinct, unique characteristics.

Old myths die hard
Because the idea of an Audubon subspecies has been promulgated for more than
a century, it has become entrenched in western mythology. “People
just eat this stuff up and keep repeating it,” Wehausen says about
the romantic notion of a “lost” species. He adds that much
incorrect information circulating about bighorn sheep doesn’t stand
up under scrutiny. “It’s frustrating for people like us, who
try to set the record straight, that the information is being ignored.”

In 2003, three years after Wehausen’s and Ramey’s study was
published, the National Bighorn Sheep Interpretive Center in Dubois, Wyoming,
exhibited an aging bighorn sheep mount labeled as the extinct Audubon’s
bighorn subspecies. The mount was on loan from South Dakota’s Custer
State Park, which labeled it as an “endemic subspecies to the badlands
and Dakotas.”

June Sampson, director of the Wyoming bighorn sheep center, justifies the
Audu-bon’s label by noting that Ramey’s and Wehausen’s
technical study can be difficult for the lay person to understand. The center
included a footnote in its information on the mount that the two scientists
concluded there never was a separate subspecies. “We let visitors decide
for themselves from there,” Sampson says.

The Dakotas and Nebraska have been especially keen on recounting the past
glory of Audubon’s bighorn. The subspecies is mentioned on the websites
of all three states’ conservation agencies. North Dakota, however,
has recently begun to publicly question the validity of the subspecies, says
Ron Wilson, editor of North Dakota Outdoors. “There is growing recognition
here that the Audubon’s designation is based on some pretty shaky science,” he
says.

Bill Jensen, a big game biologist with the North Dakota Game and Fish Depart-ment,
has collected bighorn skulls and skull measurements since the mid-1980s,
when he first grew suspicious that there was no separate subspecies.

“This all stems back to an era when a naturalist gained fame by naming
new species and subspecies,” Jensen says. “We had naturalists
running all over the place trying to name new animals. At one time, they
actually thought there were 20 different subspecies of black bear.”

Montanans aren’t immune to the Audubon’s bighorn mystique. Full
mounts of what are called Audubon’s bighorn sheep can also be found
in Havre at the Montana State University–Northern’s science building
and in Miles City’s Montana Bar.

Symbol of Paradise Lost?
Michael Sexson, a professor of mythology at Montana State University, says
no matter what the facts are, the myth of Audubon’s bighorn will
likely survive.

“Some people would prefer to believe in things more interesting than
the facts allow them to be,” he says. “We like to have our stories
as stories.”

Sexson says the sheep play an important role in the story of Lewis and Clark’s
journey across the West, an epic adventure that has become part of American
mythology. The two heroic characters overcame enormous odds to voyage from
the mouth of the Missouri River to the Pacific Ocean and back. It’s
a tale of bravery, perseverance, and faith. Yet, like other heroic myths,
the Lewis and Clark adventure has its dark side.

“As the adventurer in traditional mythology forges ahead to a new
civilization, he typically wreaks havoc on the land and leaves carnage in
his wake,” Sexson says. In the case of the Lewis and Clark saga, the
unspoiled paradise discovered by the Corps of Discovery was degraded in
the subsequent scramble for precious metals, timber, grazing lands, and farmland.
Hence, the mythologist explains, within the larger myth of the Lewis and
Clark Expedition, Audubon’s bighorn emerges as a corollary myth of
how westward exploration and eventual expansion led to the demise of the
badlands bighorn sheep.

Seen in this way, Audubon’s bighorn symbolizes both abundance and
loss. It stands for the great natural wealth America possessed when the West
was young, an Eden of bountiful forests and wildlife where native people
lived harmoniously with their natural surroundings. But it can also represent
how Americans exploited the nation’s finite natural resources in their
quest for higher living standards.

Because both views of western expansion are widely popular, Audubon’s
bighorn will likely live on—even though, as some now say, it never
even existed.